There is known a tube-and-plate heat exchanger used in the constructions of water-to-air coolers installed in motor vehicles, tractors and diesel locomotives. This type of heat exchanger comprises a plurality of plain round tubes for the passage of a cooled working fluid. These tubes are received in respective through holes formed in flat cooled plates. The tubes for the passage of a working fluid can be arranged either in parallel rows or in staggered manner. Thus, the coolers of this type are constructed so as to permit plain rectangular passages or channels to be formed in the intertubular space thereof. These channels or passages are not provided with vortex generators required to intensify the heat exchanging process in the intertubular space. This intensification of the heat exchanging process is necessitated because of the limitation that water-to-air coolers of various power plants operate under conditions where the over-all heat transfer coefficient K of the cooler is approximately equal to the air heat emission coefficient .alpha., i.e. K.apprxeq..alpha..sub.1. Therefore, a reduction in size and weight of the water-to-air cooler calls for the increase in K, which is single-valued as .alpha..sub.1. The value of .alpha..sub.1 is known to be the smallest in plain passages. Therefore, the prior-art tube-and-plate heat exchanger is large in size and weight.
The tube-and-plate heat exchangers of the aforedescribed construction can be reduced in size and weight only by increasing the heat emission coefficient .alpha..sub.1, which is possible by producing air flow turbulence in the cooler with the aid of various vortex generating means.
There is also known in the art a tube-and-plate heat exchanger (see a book by V.Z. Babichev "Manufacture of Automobile Radiators", published in 1958, Mashgiz Publishers, Moscow, p, 47) which comprises plain tubes for the passage of cooled water, the tubes being arranged either in parallel rows or in staggered fashion. In order to intensify the process of convective heat exchange in the intertubular space, the cooled plates are profiled, in the travelling direction of air flow, so as to form a continuous symmetrical waved line. The cooled plates are arranged on the cooler tube bundle so that projections and depressions of each pair of the adjacent plates are equidistant from one another. As a result, there are formed, in the interspace between the adjacent cooled plates, passages for cooling air, which have undulatory shape if viewed in the travelling direction of the air flow.
The known water-to-air coolers have been tested to show insufficiently high thermohydraulic effectiveness. The reason for this is that the increase in the heat emission coefficient .alpha..sub.1 in such passages is lagging very much behind that of the energy input required for stepping up the process of heat transfer as compared with smooth passages. This is because vortices, formed by a flow of air behind and before each turn in such passages, are equal to, or commensurate with, the height of projection of the waving passage. It should be added that the height of the projection in these types of passages is equal to, or commensurate with, the hydraulic passage diameter. As a result, the amount of energy delivered to the cooled air in waving passages is lost (by 70 to 80%) to effect transition to turbulence in the core of the flow where the temperature field gradient and that of the heat flow density are small enough to bring about any substantial increase in the heat flow density. Since these large-scale vortices possess considerable kinetic energy, they, on overcoming the forces of viscosity and friction and thus gradually dissociating, are thereafter displaced to merge with the wall layer of air. This results in the wall layer becoming turbulent, with the turbulence heat conduction and the heat flow density increasing therein. Therefore, the heat exchange process in the waving passage is intensified by the turbulence of the wall layer of the air flow and not in its core, though the loss of additional energy fed to the air flow in the waving passage so as to induce turbulence in the core of the flow is much greater than that required to produce turbulence in the wall layer thereof. And this is the main reason for low thermohydraulic effectiveness of the heat exchanging surface of the prior-art tube-and-plate heat exchanger.